1. Field of the Invention
The present invention relates to an electrical resistance element of the molybdenum silicide type.
2. Description of the Related Art
Such elements have long been known in different forms with regard to their different alloy contents. Kanthal AB of Sweden are manufacturers of such elements. These types of elements are referred to as molybdenum silicide-type elements, which have long been used to heat ovens and different kinds of surfaces, such as a radiating surface that radiates onto an object, or cooker plates, or other surfaces.
Molybdenum silicide elements are produced in different forms. A typical form is a so-called leg element, which comprises two legs that extend between two electrical conductors or terminals at one of their ends. The legs are joined with an arcuate or curved part at their other ends. The leg elements can consist of one, two, or more legs. Two-legged elements, or multi-leg elements, include one or more curved parts that extend between the conductors. The leg constitutes a glow zone, i.e., that part of the element that glows when supplied with electric current, and therewith delivers heat to an object.
One problem experienced with industrial furnaces, ovens, and the like resides in the difficulty at times of maintaining a sufficiently uniform temperature distribution in a furnace space, or in achieving sufficiently uniform thermal radiation from a radiating surface. An uneven temperature distribution or uneven radiation will mean that the space or the object to be heated will not be heated uniformly, which can be highly problematic.
A concrete example is when liquid-metal ladles are to be pre-heated. Uneven heating of a ladle presents a problem when using resistance elements, as the bottom of the ladle will not be as hot as the inner walls of the ladle.
The known method of attempting to resolve this problem involves the installation of a number of elements or groups of elements that can be controlled individually, so that different elements have delivered power of different high magnitudes.
The present invention solves the problem caused by uneven heating.